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X-RAY FLUORESCENCE SPECTROMETRY

A method of chemical analysis in which the sample is bombarded by very hard X-rays or gamma-rays, and secondary radiations, characteristic of the elements present, are studied spectro

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X-RAY FOCAL SPOT

That small area of the target anode of an X-ray tube on which the electron beam is incident, and from which emitted X-rays emerge. High- power tubes frequently have a line focus to minimize localization of the heat dissipated at the anode.

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X-RAY LASER

A laser with an output in the X-ray region of the spectrum. Using highly ionized selenium plasma as the lasing medium, laser output at 20-6 and 20-9 nm has been recently reported.

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X-RAY MICROSCOPE

Microscope using soft X-rays and a Fresnel zone plate as the focusing device; a resolution of 200 nm has been obtained using a scanning technique. The zone plate is made using a scanning transmission electron microscope, and synchrotron radiation is used as the source of X-rays. See panel on Electron microscope.

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X-RAY PHOTON

A quantum of X-ray energy given by hv, where v is the frequency and h is Planck's constant.

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X-RAY RADIOGRAPHY

The use of photographic film, often with an image intensifier screen, to record the intensities of X-rays which have passed through tissue in medicine or eg some mechanical structure in engineering. The X-rays are emitted by essentially a point source and the image is the shadow formed by the specimen.

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X-RAY SOURCE

One of several sources of cosmic X-rays: 1 the solar corona; 2 interacting binary stars, in which one member is a black hole or neutron star: 3 supernova remnants, such as the Crab Nebula; 4 some radio galaxies, such as Cygnus A. some Seyfert galaxies and some quasars. See panels on Black hole and Quasar.

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X-RAY SPECTROMETER

The name originally used for the X-ray diffractometer, but now abandoned in order to avoid confusion with X-ray fluorescent spectrometry/.

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X-RAY TELESCOPE

An instrument deployed at high altitude by balloon, rocket or spacecraft to detect and record cosmic X-rays from space. To focus the X-rays by mirrors, grazing incidence techniques are used. X-ray detectors include gas counters and scintillation counters. See panel on Astronomical telescope

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X-RAY THERAPY

The use of X-rays for medical treatment.

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